The present invention relates to a bookbinding apparatus and bookbinding system for forming a booklet by coating adhesive on the edge (spine) of a plurality of stacked sheets, particularly to a bookbinding apparatus and bookbinding system wherein adhesive is coated for each booklet.
There is a conventionally known bookbinding apparatus wherein adhesive is coated on each booklet and sheets are formed in a bundle, and this apparatus is used in a bookbinding system wherein all operations from image forming to bookbinding are performed in an integrated manner. In such a bookbinding apparatus, a hot melt adhesive is used as an adhesive, and adhesive pellets (solid glue) are supplied little by little in response to the amount consumed in coating, whereby bookbinding operation is performed on a continuous basis. In Unexamined Japanese Patent Application Publication No. 2004-209746, disclosed a supply apparatus wherein adhesive is coated on the sheet bundle by the traveling of a coating roller along the spine of a sheet bundle, and a predetermined amount of adhesive pellets are supplied little by little in units of several pellets into the melt adhesive tank wherein the coating roller is immersed.
In the Unexamined Japanese Patent Application Publication No. 2004-209746, when the amount of adhesive in the adhesive tank has been reduced, pellets are supplied in predetermined amount, whereby the liquid level of the adhesive is kept constant.
However, the bookbinding apparatus of the Unexamined Japanese Patent Application Publication No. 2004-209746 is designed in such a way that the solid glue is directly put into the melt glue portion wherein a coating roller is immersed. Thus, the half-melt solid glue is dipped up by the coating roller, and reaches the glue applied portion wherein the spine portion of the booklet conveyed comes in contact with the coating roller, with the result that a bookbinding failure occurs.
Further, there is an attempt having been made so that the solid glue conveyance distance from the position for supplying solid glue into the melting tank, to the coating roller is set to a long distance so that the solid glue having been melted sufficiently inside the melting tank is supplied to the coating roller. This attempt, however, increases the size of the melting tank and the volume of evaporation of the melted glue inside the melting tank. This problem also leads to an increase in the melting warm-up time of the solid glue at the start of bookbinding.